ZGM is a large tumor associated glycoprotein of demonstrable usefulness. Circulating levels of ZGM appear to reach a "lid" of 150ng/ml, presumably because of its large size. We are now seeking a smaller molecule with ZGM activity. The purpose of this project is to isolate the circulating subunits of ZGM for incorporation in a ZGM radioimmunoassay for improved clinical use. ZGM will be isolated from the plasma of patients with adenocarcinomas and will be compared with ZGM isolated from tumor tissues using immunochemical and physicochemical procedures. Tumor tissue ZGM will be degraded by use of hyaluronidase and neuraminidase, and treatment with sodium dodecyl sulfate, dithiothreitol, and trypsin. The subunits obtained will be radiolabeled, compared with radiolabeled plasma ZGM, and examined for differing inhibitory activity in the ZGM-RIA. We will select from plasma ZGM a ligand for measuring circulating ZGM more specific and sensitive than that isolated from tumor tissue. The clinical usefulness of the new ZGM-RIA will be tested in patients and compared with CEA-RIA analysis.